The present invention is directed to an atherectomy catheter, particularly, a distal atherectomy catheter for use in the distal and coronary arteries where small vessel size and tortuosity present numerous problems of access.
Many technological advancements have been made in recent years for treatment of coronary disease. Surgical bypass techniques, such as coronary artery bypass graft surgery, are routinely performed and are highly successful. While the risks of bypass surgery have been minimized through technological advancements, opening of the chest cavity is still required. This requires special surgical skills and equipment which are not readily available in many areas. For many patients, a bypass operation may not be indicated and therefore various surgical techniques have been devised to treat occlusive coronary artery diseases of such patients. For example, various prior art devices have been developed for removing and/or compressing atherosclerotic plaque, thromboses, stenosis, occlusion, clots, embolic material, etc. from veins, arteries and the like.
One such device is disclosed in applicant's co-pending U.S. patent application Ser. No. 07/833,362 filed Feb. 10, 1992, which disclosure is incorporated by reference herein. In applicant's application, removal of occlusive material is accomplished by a reciprocal rotary cutter head mounted at the distal end of a catheter tube for excising occlusive material blocking the coronary vessel.
While the apparatus of applicant's application has been successfully shown to remove occlusive material in laboratory tests, enhanced and more efficient removal of occlusive material may be achieved with the improved apparatus described herein. One feature which is important to the acceptability of a distal atherectomy catheter by the medical community is the efficiency and speed with which the lumen of an artery or the like may be unblocked to provide normal blood flow.
U.S. Pat. No. 4,650,466 (Luther) discloses an angioplasty device comprising a woven tube of metal or plastic fibers and a retraction stylet that are attached at one end of the catheter tube for insertion into a vein, artery, and the like for the removal of plaque and similar materials. One or more guide wires are attached to the woven tube for rotation and manipulation inside the artery. The woven tube is placed within the artery and expanded to contact the interior, plaque coated, wall of the artery. Movement of the expanded woven tube abrades the plaque from the arterial wall to form particles which are trapped within the woven tubes. The trapped plaque particles are removed with the angioplasty device upon its removal from the artery of the patient.
Other prior art devices include catheters fitted with an inflatable balloon for compressing occlusive materials such as plaque against the vessel wall. U.S. Pat. No. 4,273,128 (Lary) discloses a coronary cutting and dilating instrument for treatment of stenotic and occlusive coronary artery disease. The device disclosed therein includes a cutting and dilating instrument having one or more radially extending knife blades at a forward end thereof for making the coronary incision and an inflatable balloon for dilating the stenotic artery zone immediately after the incision.
Other angioplasty devices include a catheter having a motor driven cutting head mounted at its distal end. The cutting head is connected to the drive motor via a flexible drive shaft extending through the catheter. Extremely high rotational cutting head speeds have been achieved, in the range of 50,000-300,000 rpm, by these motor driven cutter heads. Various problems, however, have been associated with the use of the balloon tipped catheters and high speed cutting heads. The balloon catheter is expanded by injection of pressurized fluid into the balloon to expand it against the wall of the artery. Some problems which have been reported include the vessel dissection, perforation, rupture, conversion of a stenosis to an occlusion, and embolization. Furthermore, angioplasty devices utilizing balloons do not remove the plaque from the arterial wall but simply compress the plaque against the wall of the vessel. Thus, the stenosis or occlusion frequently reoccur requiring further treatment.
Atherectomy devices utilizing a motor driven high speed cutting head include a number of disadvantages. Heat dissipation and vibration is a problem. The path of the occlusion in an artery is often a tortuous path and therefore the lengthy flexible drive shaft connected to the cutter head must traverse a number of bends or curves. Consequently, as the flexible drive shaft rotates, it contacts the inner wall of the catheter resulting in localized heating and vibrations due to the frictional contact. This, of course, is very uncomfortable for the patient and may result in spasm, weakening or perforation of the vessel along the route of the catheter.
It is therefore one advantage of the present invention to provide an improved atherectomy catheter having a reciprocal rotary cutter head at the distal end thereof rotated at a relatively low speed in the range of 2,000 rpm to enhance patient comfort.
One notable feature of the invention to provide an atherectomy catheter for traversing the small and tortuous vasculature of the heart while having the ability is to bore through a total obstruction and excise a hemispherical or circumferential section from the lumen of the vessel and entrap the excised section within a containment housing.
It is yet another object of the invention to provide an atherectomy catheter for progressively opening the lumen of a vessel, entrapping and discharging the excised obstructive material into a containment housing or discharge passage of the catheter until the entire obstruction has been removed leaving a smooth fissure and flap-free enlarged internal vessel diameter.